1. Field of the Invention
The present invention relates to an extra length accommodation structure for optical fibers in a communication device.
2. Description of the Related Art
In recent years, a transmission line for a communication device has been changed from an electrical cable (coaxial cable or twisted cable) to an optical cable. Particularly in a communication device related to Fiber To The Home (FTTH), a size reduction of the communication device is being pursued in consideration of an introduction of the communication device into every home. However, the workability in connecting an optical cable to the communication device is reduced by the size reduction, so it is necessary to provide a structure which can easily accommodate an extra length of optical fibers.
As mentioned above, in an FTTH related communication device, it is required to reduce the size of the communication device in consideration of an introduction of the communication device into every home, and accordingly high-density packaging of the communication device is also being pursued. In association with this, it is also required to reduce the size of the extra length accommodation structure for optical fibers for space saving. However, the size reduction of the extra length accommodation structure for optical fibers is limited because the optical fiber has an allowable minimum radius of curvature. If the size of the structure is forcibly reduced within this limit, the workability in accommodating the extra length of the optical fibers is reduced.
In the case of developing a compact desktop communication device for introducing an external optical cable, it is accordingly necessary to design an extra length accommodation structure for optical fibers which occupies a minimum space and provides good workability. The external optical cable to be introduced into the communication device is an optical cable having holder lines. Accordingly, the communication device has a fixing portion for fixing each holder line extending from the optical cable. The extra length of the optical fiber extending from the optical cable fixed by the fixing portion is wound around an optical fiber winding portion to thereby accommodate the extra length.
A free end of the optical fiber wound around the optical fiber winding portion is spliced to one end of another optical fiber connected at its other end to an optical connector. The conventional extra length accommodation structure has a splicing portion accommodation structure for accommodating such a splicing portion for splicing the two optical fibers. Thus, the extra length of the optical fiber is first wound around the winding portion, and the splicing portion is next accommodated into the splicing portion accommodation structure. In many cases, however, the length of the optical fiber wound around the winding portion does not become a suitable length for accommodation of the splicing portion. It is accordingly necessary to adjust the length of the optical fiber wound by adjusting a degree of tightness of winding of the optical fiber.
In the conventional extra length accommodation structure, there is not defined a space for ensuring a sufficient extra length of the optical fiber in winding the optical fiber because of the reduced size of the communication device. Accordingly, the length of the optical fiber extending from the fiber winding portion and connected to the optical connector must be adjusted at the winding portion, so as to engage the optical connector with another connector provided in the communication device. Thus, fine adjustment of the length of the optical fiber extending from the winding portion is required. This fine adjustment requires an additional operation of loosening the optical fiber once wound around the winding portion or rewinding the optical fiber.
Further, since the optical fiber is often loosely wound around the winding portion, a plurality of optical fiber pressure plates are provided to prevent escape of the optical fiber from the winding portion. These optical fiber pressure plates further reduce the workability in winding the optical fiber. In the conventional extra length accommodation structure, the optical fiber extending from the external optical cable and the optical fiber connected to the optical connector are wound around the common winding portion. Accordingly, in the case of checking optical input as to handle any troubles, there is a possibility that all the optical fibers must be unwound from the winding portion if the optical fiber connected to the optical connector is wound earlier than the other optical fiber.